Code review comment for lp:~vthompson/music-app/proceeds-to-next

I'll move the tests to the end for now, as I assume it's the best answer. One thing we need to figure out is whether this will work once the media-hub's tracklist implementation lands. When the song switches to the next track everything will be handled in the media hub. We need to determine if 1) media hub will alert the app when the song changes and 2) can autopilot retrieve app components and properties when the app is suspended.